Five score for former county division (7)
I believe the answer is:
hundred
I believe this clue is a double definition.
'five score' is the first definition.
(five twenties)
'former county division' is the second definition.
'for' acts as a link.
(Other definitions for hundred that I've seen before include "entirely associated with 27 [PERCENT]" , "Old subdivision of a shire or county" , "Historical division of a county - number" , "Square number" , "Former division of county" .)